L-325 Sagebrush Habitat Mitigation Project: Final Compensation Area Monitoring Report

This document provides a review and status of activities conducted in support of the Fluor Daniel Hanford Company (Fluor), now Mission Support Alliance (MSA), Mitigation Action Plan (MAP) for Project L-325, Electrical Utility Upgrades (2007). Three plantings have been installed on a 4.5-hectare mitigation area to date. This review provides a description and chronology of events, monitoring results, and mitigative actions through fiscal year (FY) 2012. Also provided is a review of the monitoring methods, transect layout, and FY 2012 monitoring activities and results for all planting years. Planting densities and performance criteria stipulated in the MAP were aimed at a desired future condition (DFC) of 10 percent mature sagebrush (Artemisia tridentata ssp wyomingensis) cover. Current recommendations for yielding this DFC are based upon a conceptual model planting of 1000 plants/ha (400/ac) exhibiting a 60-percent survival rate after 5 monitoring years (DOE 2003). Accordingly, a DFC after 5 monitoring years would not be less than 600 plants/ha (240/ac). To date, about 8700 sagebrush plants have been grown and transplanted onto the mitigation site. Harsh site conditions and low seedling survival have resulted in an estimated 489 transplants/ha on the mitigation site, which is 111 plants/ha short of the target DFC. Despite this apparent shortcoming, 71, 91, and 24 percent of the surviving seedlings planted in FY 2007 and FY 2008 and FY 2010, respectively, showed signs of blooming in FY 2012. Blooming status may be a positive indication of future sagebrush recruitment, and is therefore a potential source for reaching the target DFC of 600 plants/ha on this mitigation site over time. Because of the difficulty establishing small transplants on this site, we propose that no additional plantings be considered for this mitigation area and to rely upon the potential recruitment by established seedlings to achieve the mitigation commitment set forth in the MAP of 600 plants/ha